You may be familiar with Scrat, the “saber-toothed squirrel” from the Ice Age movies, but a real one lives in Niagara Falls, New York. This squirrel has an unusual tusk growing out of its lower jaw! Mary Jo Sutter has been feeding the squirrel since it was young. Watch the video of the squirrel who has no fear of humans or cats. Link

He reminds me of a house finch who visited my feeders years ago. His upper beak was either undeveloped or damaged, and his lower beak grew out like a sword.I felt sorry for him at first, until I noticed that no bird dared to squabble with him. He ate as much as he wanted. The other birds had to wait.

As another commenter mentioned at the page, one of the squirrels bottom teeth probably grew in at an angle, so that it wasn't worn down like the other teeth (the front teeth of rodents continue to grow throughout their lives and are kept short by gnawing).

Which, you know, whatever, it's cool. As long as the squirrel gets along, and she seems to.